Non-alcoholic steatohepatitis (NASH) is an extreme form of non-alcoholic fatty liver disease (NAFLD), a condition resembling alcohol-induced liver injury associated with obesity and metabolic syndrome rather than alcohol abuse. In NAFLD, triglycerides accumulate within hepatocytes due to alterations in lipid synthesis, storage, movement, or clearance processes causing steatosis. While steatosis typically has no large risk implications on its own, in a subset of NAFLD patients the steatosis progresses to include inflammation (hepatitis), necrosis and fibrosis, a condition known as NASH. These NASH patients have highly elevated risks of both hepatocellular carcinoma (HCC, as high as 7.6% total risk in one study) and cirrhosis (as high as 25% total risk), ultimately leading to liver failure or death.
Current population-based studies indicate that at least 25% of the US population has NAFLD and about 25% of NAFLD patients will go on to develop NASH, making these conditions a significant epidemiologic contributor to organ failure and cancer. As these conditions are associated with obesity and metabolic disease, their prevalence is likely to increase in the future.